Facebook has added a new feature to its mobile app as of Wednesday that uses a phone's microphone to identify ambient TV shows, music, or movies and include them in status updates. The feature is off by default, though the app offers to turn it on in an intro screen that it pops up for users.

Facebook has lately made a push into encouraging its users to talk about trends by introducing hashtags and a list of topics people are discussing on the site (Nicki Minaj, Aaron Hernandez, and Petco are some on this reporter's news feed, presently). The microphone trick is likely meant to make status updates more uniform so that cataloging can be more seamless. But it works passively, not on command, so any time a user writes a status update, their phone will be listening to surrounding noise.

The feature works similar to that of the music-identification service Shazam: the phone listens for 30 seconds, and then the app will pop up its best guess for the music or video it's hearing. "If you’ve turned the feature on, you’ll see an audio icon moving on the screen when you write a status update. If the feature finds a match, you can then choose to add the song, TV show, or movie to your post," states Facebook's blog post. Identified music will be attached to the status update as a 30-second clip, and TV shows will be identified by the episode and season.

Facebook specifies that it will not store any audio it doesn't identify as an existing piece of content, and it stresses that the feature is optional. Though it's worth noting that many Facebook features are optional, until such a time as they are not.